One thing to keep in mind if you make your own ballast is that it's laminants are made from an alloy (silicon steel, I think) that's coated with an insulative coating, to reduce eddy currents.
Sounds like your coil is similar to mine, as far as size. 14.4 kV, 25 kVA pig, bombarder ballast, 10.25" x 72" 18 AWG secondary.
I have a 16" PVC pipe that will be my next upgrade. I also bought 16" corrugated drainage pipe for a topload. I paid hundreds of dollars for pretty spun toroids, but I've outgrown them.
From: Buds tape mail <bud@xxxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Friday, July 31, 2015 8:21 AM
Subject: Re: [TCML] Variable Ballast
Hi Phil and others, I have been reading thru your web site and Richie's
very thoroughly. I have built a 12" X 51" secondary #18 wire and have
finished a 56" toroid and will have this thing ready to go very soon. I
have a rotary spark gap (copy of Ed's in Rochester) and a 14kv pole pig. I
have been reading extensively about primary inductive ballast. I do have
two 225 amp buzz boxes I could use in parallel as ballast like others have
done. I understand the principle series on the primary side limiting the
power to the pig.
I saw how and why you wound your own ballast. My question is
this........can we just use a very large welding transformer........say 400
amp unit as the ballast while shorting the secondary or should we just bite
the bullet and wind a huge ballast from an older transformer with a huge
iron core? I have my own machine shop.......... www.tape-inc.com
..........and can do almost anything once I know what it is I need to do. I
think most of us do not know the how and whys of ballast design.....you know
the core size min/max and wire size min/max for a pig of this size.
Bud Mohrman
-----Original Message-----
From: Phil
Sent: Friday, July 31, 2015 5:16 AM
To: 'Yurtle Turtle' ; 'Tesla Coil Mailing List'
Subject: Re: [TCML] Variable Ballast
Jon,
The modern cheap import ones you see knocking about are generally not up to
the job for a pole pig, without getting pretty hot during use. I melted and
shorted the windings of one a while back while running @ 10.5kv / 400mA -
(hardly pig output) simply because I left it running for several minutes
(they normally have a thermal cutout to disconnect the mains input during
normal use)
Their duty cycle is very low sometimes, especially as Yurtle mentions, if
Alu' conductor is used; also the resulting voltage drop from lossy windings
gets multiplied up by the pig, so you could potentially be losing 0.5kv at
the worst case.
Winding your own ballast is a better option.
Regards
Phil Tuck
www.hvtesla.com
-----Original Message-----
From: Tesla [mailto:tesla-bounces@xxxxxxxxxx] On Behalf Of Yurtle Turtle via
Tesla
Sent: 30 July 2015 20:52
To: GENE GARRAGE; Tesla Coil Mailing List; Tesla Coil Mailing List
Subject: Re: [TCML] Variable Ballast
I got a 225 amp Lincoln welder at a garage sale.It was old enough to have
copper windings. I chose to short the welding leads internally, and
eliminate the cables.
From: GENE GARRAGE via Tesla <tesla@xxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Wednesday, July 29, 2015 6:53 PM
Subject: Re: [TCML] Variable Ballast
From: Jon Danniken <danniken@xxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Thursday, July 2, 2015 2:28 PM
Subject: Re: [TCML] Variable Ballast
On 07/01/2015 11:14 AM, Miles Mauldin wrote:
> Do I need to find an old welder, or will an inexpensive new one work
> just as well. Read many posts about shorting the secondary and using
> the primary in line with a pole pig. Thoughts, ideas or suggestions
> all wanted for a variable ballast.
You can get an old 220V arc welder for cheap on craigslist if you are
patient, less cheap if you are not patient. As a bonus, you also get a
welder.
Jon
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